In wireless local area networks (WLAN), for example, WLANs that are based on IEEE-802.11-1999 standard, a wideband (WB) Orthogonal Frequency Division Multiplexing (OFDM) modulation schemes or duplex time division multiplexing (TDM) modulation schemes may be used. In those systems the data rate and throughput of network may be increased by increasing spectrum bandwidth of transmitted signals and/or by using several OFDM channels in parallel and/or by applying adaptive bit and power loading (BPL) information to a data packet, if desired. An OFDM signal may include a predefined number of sub-carriers pilot signals, for example, 16 sub-carriers. The WLAN may include stations that may transmit data packets acting over a non-stationary frequency-selective shared wireless medium, which may be referred to as “channel”.
For example, transmission of data packed may be done by the stations in-doors. Under these conditions the signal propagation may include multi-path and non-stationary characteristics. The multi-path may be caused by multiple scatters, for example, walls, ceilings, and various objects, and may result in frequency selectivity of a channel transfer function. Non-stationarity may be caused by motion of scattering objects resulting in Doppler shift of received signal frequency. An additional non-stationarity may be caused by unpredictable behavior of interferences in the same band as the data packet. These factors may result in greater Packet Error Rate (PER) and significantly reduce the throughput performance of wireless network.
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